Valve releases Team Fortress 2 source code to modders for free game development

Valve has released the Team Fortress 2 source code to modders through the Source software development kit (SDK). This allows fans to create and publish new games based on TF2, but all content must be free of charge. Modders can make significant changes to the game, from small tweaks to complete overhauls. However, they must respect the contributions of the Steam Workshop community and cannot profit from their mods. In addition to the TF2 source code, Valve is updating other games using the Source engine. These updates include 64-bit support and improvements to user interfaces for titles like Half-Life 2 and Counter-Strike: Source.